Routing bridges (“RBridges”), as defined in the Internet Engineering Task Force (IETF) Request for Comments (RFC) 6325, may be configured to manage network communications of one or more physical servers. The physical servers in the network may be arranged in a plurality of data centers, and they may host one or more virtual machines. Thus, the RBridges that manage the network communications of the physical servers may also manage communications of the one or more virtual machines.
Virtual machines may “move” within the network when they are reassigned or otherwise hosted by different physical servers. The virtual machines may send communications (e.g., packets) to each other. In one example, when virtual machines are hosted by physical servers that are in the same data center, the virtual machines may communicate with each other directly (via the RBridges in the data center) by sending packets to the addresses associated with each of the virtual machines. In another example, when virtual machines are hosted by physical servers that are in different data centers, the virtual machines may communicate with each other indirectly by sending packets to a border RBridge in one data center to route the packets to another border RBridge in another data center. In this latter example, the virtual machines may send the packets to the border RBridges based on routing information (called a host route) that identifies the next hop border RBridge and the communication path for communications between the virtual machines.